A known problem of operating an internal combustion engine is the generation of harmful nitrogen oxides. Those nitrogen oxides may form during combustion as a result of high peak combustion temperatures. Accordingly, reducing the peak combustion temperatures during combustion may generally reduce the formation of nitrogen oxides. For this reason, lean air fuel mixtures such as lean gaseous fuel air mixtures are used. A lean air fuel mixture has a relatively large air-to-fuel ratio compared to a fuel mixture having stoichiometric air-to-fuel ratio.
Operating an internal combustion engine with a relatively large air to fuel ratio (lean mixture) may result in an incomplete combustion within the main combustion chamber due to the relatively slow rate of flame propagation from a single point ignition source, such as a spark plug. Furthermore, a poor ignitability may result from the lean mixture. Particularly, large-bore engines may suffer from those effects.
To improve the ignitability of lean burn gaseous fuel internal combustion engines, the same may be provided with pre-chambers (also referred to as pre-combustion chambers). For example, such a pre-chamber may be fluidly connected to a main combustion chamber of a respective cylinder via, for example, a plurality of flow transfer passages, but at least one. Those flow transfer passages allow flow of a lean mixture of gaseous fuel and air from the main combustion chamber into the pre-chamber during a compression stroke. Enrichment of the lean mixture in the pre-chamber is typically effected by providing a small quantity of gaseous fuel into the pre-chamber via a separate gas feed passage. The enriched mixture is ignited in the pre-chamber by an igniter such as a spark plug. Ignition of the enriched mixture causes a flame front of hot gases that propagates from the pre-chamber via the flow transfer passages into the main combustion chamber. Thus, the lean mixture in the main combustion chamber ignites and burns, and, thereby, expands against a movable piston that drives a crankshaft.
For example, U.S. Pat. No. 5,024,193 of Caterpillar Inc. discloses a fuel combustion system with a pre-combustion chamber assembly defining a pre-chamber. The pre-chamber has a pre-selected shape and volume. A plurality of ejection passages of pre-selected geometric cross-section is provided for directing and controllably expanding burning gases from the pre-chamber into a main combustion chamber at a velocity greater than speed of sound.
The present disclosure is directed, at least in part, to improving or overcoming one or more aspects of prior systems.